The present invention relates to special stereorigid metallocene compounds and a process for the preparation of polyolefins in the presence of these special stereorigid metallocene compounds.
The literature discloses the preparation of polyolefins using soluble metallocene compounds in combination with aluminoxanes or other cocatalysts which, owing to their Lewis acidity, can convert the neutral metallocene into a cation and stabilize it (EP 129 368, EP 351 392).
The conference volume of the 1st Journal of organometallic Chemistry Conference on Applied Organometallic Chemistry, page 136, describes metallocenes which have a substituted tricyclic hydrocarbon as a ligand system.
The use of soluble metallocene compounds based on bis(cyclopentadienyl)zirconiumdialkyl or bis(cyclopentadienyl)zirconium dihalide in combination with oligomeric aluminoxanes gives atactic polymers which, owing to their unbalanced and inadequate product properties, are only of little importance industrially. Moreover, certain olefin copolymers are not obtainable.
Derivatives of zirconocene dichloride in which the two substituted cyclopentadienyl groups are linked to one another via a methylene, ethylene or dimethylsilylene bridge can, owing to their conformational rigidity, be used as catalysts for the isospecific polymerization of olefins (Chem. Lett. (1989), 1853 to 1856 or EP A 0 316 155). Metallocenes having (substituted) indenyl radicals as ligands are of particular importance for the preparation of highly isotactic polymers having high crystallinity and a high melting point (EP 485 823, EP 530 647).
Also of major interest are polyolefins whose property profile is between these two extremes.
It is an object of the present invention to provide a metallocene compound which avoids the disadvantages of the prior art and is suitable for the preparation of polyolefins.
We have found that this object is achieved by a stereorigid metallocene compound of the formula I 
where
M is a metal of Group IIlb, IVb, Vb or VIb of the Periodic Table of the Elements,
R1 and R2 are identical or different and are each hydrogen, a C1-C40-hydrocarbon-containing group, such as C1-C10-alkyl, C1-C10-alkoxy, C6-C10-aryl, C6-C25-aryloxy, C2-C10-alkenyl, C7-C40-arylalkyl or C7-C40-arylalkenyl, OH, halogen or NR1521 where R15 is halogen, C1-C10-alkyl or C6-C10-aryl, or R1 and R2, together with the atoms linking them, form a ring system,
R3, R4, R5, R6, R7, R8, R9, R10, R11, R14, R15 and R16 are identical or different and are each hydrogen, a C1-C40-hydrocarbon-containing-group, such as C1-C10-alkyl, which may be halogenated, C6-C30-aryl, which may be halogenated, C6-C20-aryloxy, C2-C12-alkenyl, C7-C40-arylalkyl, C7-C40-alkylaryl or C8-C40-arylalkenyl, halogen, SiR173, NR172, SiOR173, SiSR173 or PR172, where R17 are identical or different and are each halogen, C1-C10-alkyl or C6-C10-aryl or form a ring system, or two or more neighboring radicals R3, R4, R5, R6, R7, R8, R9, R10, R11 , R14, R15 and R16, together with the atoms linking them, form a ring system which preferably contains 4 to 40, particularly preferably 6 to 20, carbon atoms,
and R12 and R13 are identical or different and are each hydrogen, a C6-C30-aryl-containing group, such as C6-C30-aryl, C6-C20-aryloxy, C7-C40-arylalkyl or C8-C40-arylalkenyl, each of which may be halogenated, and at least one of the radicals R12 and R13 is not hydrogen.
In compounds of the formula I
M is preferably a metal of Group IVb of the Periodic Table of the Elements, such as titanium, zirconium or hafnium, in particular zirconium,
R1 and R2 are identical and are each C1-C4-alkyl or halogen, such as fluorine, chlorine, bromine or iodine, in particular chlorine,
R3, R4, R5, R6, R7, R8, R9, R10, R11, R14, R15 and R16 are identical or different and are each hydrogen, C1-C10-alkyl or C6-C24-aryl, or two or more neighboring radicals R3, R4, R5, R6, R7, R8, R9, R10, R11, R14, R15 and R16, together with the atoms linking them, form an aromatic or aliphatic ring system of 4 to 20 carbon atoms,
and R12 and R13 are identical or different and are each hydrogen or C6-C24-aryl and at least one of the radicals R12 and R13 is not hydrogen.
Compounds of the formula I where
M is zirconium,
R1 and R2 are identical and are each halogen, in particular chlorine,
R3, R4, R5, R6, R7, R8, R9, R10, R11, R14, R15 and R16 are identical or different and are each hydrogen, C1-C4-alkyl, such as methyl, ethyl, propyl, isopropyl, butyl, tert-butyl or isobutyl, or C6-C14-aryl, such as phenyl or naphthyl, or R11 and R15 form a ring system, and R12 is hydrogen and R13 is C6-C14-aryl, are particularly preferred.
Examples of novel metallocene compounds are:
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-phenyl-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-phenyl-xcex75-cyclopentadienyl)-(9-fluorenyl)]-dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-phenyl-h5-tetrahydropentalene]dichlorotitanium
[Isopropylidene-(2-phenyl-xcex75-cyclopentadienyl)-(9-fluorenyl)]-dichlorotitanium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-phenyl-h5-tetrahydropentalene]dichlorohafnium
[Isopropylidene-(2-phenyl-xcex75-cyclopentadienyl)-(9-fluorenyl)]-dichlorohafnium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-phenyl-h5-tetrahydropentalene]bisdimethylaminozirconium
[Isopropylidene-(2-phenyl-xcex75-cyclopentadienyl)-(9-fluorenyl)]bisdimethylaminozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(p-tolyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(p-tolyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]-dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(m-tolyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(m-tolyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]-dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(o-tolyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(o-tolyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]-dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(2,3-dimethylphenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(2,3-dimethylphenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(2,4-dimethylphenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(2,4-dimethylphenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(2,6-dimethylphenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(2,6-dimethylphenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(3,5-dimethylphenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(3,5-dimethylphenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-tetramethylphenyl-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-tetramethylphenyl-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-tetramethylphenyl-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-tetramethylphenyl-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(2,4-dimethoxyphenyl)-h5-tetrahydropentalene]dichlorozirconium [Isopropylidene-(2-(2,4-dimethoxyphenyl)-n5-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(3,5-dimethoxyphenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(3,5-dimethoxyphenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium,
[Isopropylidene-(2-(2,3-dimethoxyphenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium,
[Isopropylidene-(2-(2,6-dimethoxyphenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(chlorophenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(chlorophenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(dichlorophenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(dichlorophenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(trichlorophenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(trichlorophenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(fluorophenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(fluorophenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(difluorophenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(difluorophenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(pentafluorophenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(pentafluorophenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(3,5-trifluoromethyl-phenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(3,5-trifluoromethyl-phenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(tert-butyl-phenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(tert-butylphenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(3,5-di-tert-butylphenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(3,5-di-tertbutylphenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(biphenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(biphenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(biphenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(biphenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-(3,5-diphenyl-phenyl)-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-(3,5-diphenyl-phenyl)-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
[4-(h5-Fluorenyl)-4,6,6-trimethyl-2-naphthyl-h5-tetrahydropentalene]dichlorozirconium
[Isopropylidene-(2-naphthyl-xcex75-cyclopentadienyl)-(9-fluorenyl)]dichlorozirconium
The nomenclature of the abovementioned novel compound is to be illustrated on the basis of the compound [4-(h5-fluorenyl)-4,6,6-trimethyl-2-phenyl-h5-tetrahydropentalene]dichlorozirconium. 
The novel metallocenes are highly active catalyst components for olefin polymerization. Depending on the substitution pattern of the ligands, the metallocenes may be obtained as an isomer mixture. The metallocenes are preferably used in the form of the pure isomer. The use of the racemate is sufficient in most cases.
However, it is also possible to use the pure enantiomer in the (+) or (xe2x88x92) form. An optically active polymer can be prepared using the pure enantiomers. However, the configurational isomers of the metallocenes should be separated since the polymerization-active center (the metal atom) in these compounds produces a polymer having different properties. This may be entirely desirable for specific applications, for example soft moldings.
The present invention also relates to a process for the preparation of a polyolefin by polymerizing at least one olefin in the presence of a catalyst which contains at least one cocatalyst and at least one stereorigid metallocene compound of the formula I. The term polymerization is understood as meaning homopolymerization as well as copolymerization.
One or more olefins of the formula Raxe2x80x94CHxe2x95x90CHxe2x80x94Rb, where Ra and Rb are identical or different and are each hydrogen or a hydrocarbon radical of 1 to 20, in particular 1 to 10, carbon atoms, and Ra and Rb, together with the atoms linking them, may form one or more rings, are preferably polymerized in the novel process. Examples of such olefins are 1-olefins of 2 to 40, preferably 2-10 carbon atoms, such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene or 1-octene, styrene, dienes, such as 1,3-butadiene, isoprene, 1,4-hexadiene or cyclic olefins.
In the novel process, preferably ethylene or propylene is homopolymerized, or ethylene is copolymerized with one or more cyclic olefins, such as norbornenes, and/or with one or more acyclic 1-olefins of 3 to 20 carbon atoms, such as propylene, and/or with one more dienes of 4 to 20 carbon atoms, such as 1,3-butadiene or 1,4-hexadiene. Examples of such copolymers are ethylene/norbornene copolymers, ethylene/propylene copolymers and ethylene/propylene/1,4-hexadiene copolymers.
The polymerization is carried out at from 60 to 250xc2x0 C., particularly preferably from 50 to 200xc2x0 C. The pressure is preferably from 0.5 to 2000, particularly preferably from 5 to 64, bar.
The polymerization can be carried out by solution, mass, suspension or gas-phase polymerization, continuously or batchwise, in one or more stages. A preferred embodiment is the gas-phase or solution polymerization.
The catalyst used in the novel process preferably contains a metallocene compound. It is also possible to use mixtures of two or more metallocene compounds, for example for the preparation of polyolefins having a broad or multimodal molar mass distribution.
In principle, every compound which, owing to its Lewis acidity, is capable of converting a neutral metallocene into a cation and stabilizing it is suitable as a cocatalyst in the. novel process (labile coordination). In addition, the cocatalyst or the anion formed from it should not undergo any further reactions with the metallocene cation formed (EP 427 697). A preferably used cocatalyst is an aluminum compound and/or a boron compound.
The boron compound is preferably of the formula R18xNH4xBR194, R18xPH4xBR194, R183CBR194 or BR193, where x is from 1 to 4, preferably 3, the radicals R18 are identical or different, preferably identical, and are each C1-C10-alkyl or C6-C18-aryl, or two radicals R18, together with the atom linking them, form a ring, and the radicals R19 are identical or different, preferably identical, and are each C6-C18-aryl which may be substituted by alkyl, haloalkyl or fluorine. In particular, R18 is ethyl, propyl, butyl or phenyl and R19 is phenyl, pentafluorophenyl, 3,5-bistrifluoromethylphenyl, mesityl, xylyl or tolyl (EP 277 003, EP 277 004 and EP 426 638).
A preferably used cocatalyst is an aluminum compound, such as aluminoxane and/or an aluminum alkyl.
A particularly preferably used cocatalyst is an aluminoxane, in particular of the formula IIa for the linear type and/or of the formula IIb for the cyclic type, 
where, in the formulae IIa and IIb, the radicals R20 are identical or different and are each hydrogen or a C1-C20-hydrocarbon group, such as C1-C,8-alkyl, C6-C18-aryl or benzyl, and p is an integer from 2 to 50, preferably from 10 to 35.
Preferably, the radicals R20 are identical and are each hydrogen, methyl, isobutyl, phenyl or benzyl, particularly preferably methyl.
If the radicals R20 are different, they are preferably methyl and hydrogen or alternatively methyl and isobutyl, hydrogen or isobutyl preferably being present in a numerical proportion of from 0.01 to 40% (of the radicals R20).
Processes for the preparation of the aluminoxanes are known. The exact three-dimensional structure of the aluminoxanes is not known (J. Am. Chem. Soc. 115 (1993), 4971).
For example, it is possible that chains and rings link to form larger two-dimensional or three-dimensional structures.
Regardless of the method of preparation, the common feature of all aluminoxane solutions is the varying content of unconverted aluminum starting compound, which is present in free form or as an adduct.
It is possible to preactivate the metallocene compound with a cocatalyst, in particular an aluminoxane, before use in the polymerization reaction. This substantially increases the polymerization activity. The preactivation of the metallocene compound is preferably carried out in solution. Preferably, the metallocene compound is dissolved in a solution of the aluminoxane in an inert hydrocarbon. A suitable inert hydrocarbon is an aliphatic or aromatic hydrocarbon. Toluene is preferably used.
The concentration of the aluminoxane in the solution is from about 1% by weight to the saturation limit, preferably from 5 to 30% by weight, based in each case on the total amount of solution. The metallocene can be used in the same concentration but is preferably used in an amount of from 10xe2x88x924 to 1 mol per mol of aluminoxane. The preactivation time is from 5 minutes to 60 hours, preferably from 5 to 60 minutes. A temperature of from 78 to 100xc2x0 C., preferably from 0 to 80xc2x0 C., is employed.
The metallocene compound is preferably used in a concentration, based on the transition metal, of from 10xe2x88x923 to 10xe2x88x928, preferably from 10xe2x88x924 to 10xe2x88x927, mol of transition metal per dm3 of solvent or per dm3 of reactor volume. The aluminoxane is preferably used in a concentration of from 10xe2x88x926 to 10xe2x88x921, preferably from 10xe2x88x925 to 10xe2x88x922, mol per dm3 of solvent or per dm3 of reactor volume. The other cocatalysts mentioned are used in roughly equimolar amounts, based on the metallocene compound. However, higher concentrations are in principle also possible.
The aluminoxane can be prepared in various ways by known processes. One of the methods comprises, for example, reacting an aluminum-hydrocarbon compound and/or a hydridoaluminum-hydrocarbon compound with water (in gaseous, solid, liquid or bound formxe2x80x94for example as water of crystallization) in an inert solvent (for example toluene). For the preparation of an aluminoxane having different radicals R20, for example, two different trialkylaluminums are reacted with water according to the desired composition.
For removing catalyst poisons present in the olefin, purification with an aluminum compound, preferably an aluminum alkyl, such as trimethylaluminum or triethylaluminum, is advantageous. Either this purification can be carried out in the polymerization system itself or the olefin is brought into contact with the aluminum compound and then separated again before being added to the polymerization system.
In the novel process, hydrogen may be added as a molar mass regulator and/or for increasing the catalyst activity. Low molecular weight polyolefins, such as waxes, can be obtained as a result.
In the novel process, the metallocene compound is preferably reacted with the cocatalyst outside the polymerization reactor in a separate step using a suitable solvent. A catalyst carrier may be provided.
In the novel process, prepolymerization can be carried out with the aid of the metallocene compound. The olefin (or one of the olefins) used in the polymerization is preferably used for the prepolymerization.
The catalyst used in the novel process may be supported. By providing a catalyst carrier, it is possible, for example, to control the particle morphology of the polyolefin prepared. The metallocene compound can be reacted first with the carrier and then with the cocatalyst. It is also possible first to apply the cocatalyst to a carrier and then to react it with the metallocene compound. It is also possible to apply the reaction product of metallocene compound and cocatalyst to a carrier. Suitable carrier materials are, for example, silica gels, aluminas, solid aluminoxane or other inorganic carrier materials, for example magnesium chloride. Another suitable carrier material is a polyolefin powder in finely divided form. The preparation of the supported cocatalyst can be carried out, for example, as described in EP 567 952.
Preferably, the cocatalyst, e.g. aluminoxane, is applied to a carrier, for example a silica gel, an alumina, a solid aluminoxane, another inorganic carrier material or a polyolefin powder in finely divided form, and then reacted with the metallocene.
The inorganic carriers used may be oxides which were produced by flame pyrolysis, by combustion of element halides in an oxyhydrogen flame, or which can be prepared as silica gels in specific particle size distributions and particle shapes.
The preparation of the supported cocatalyst can be carried out, for example as described in EP 578 838, in the following manner in an explosion-proof stainless steel reactor having a pumping system for a pressure level of 60 bar, an inert gas supply, thermostating by jacket cooling and a second cooling circulation via a heat exchanger in the pumping system. The pumping system sucks in the reactor content via a connection in the reactor bottom by means of a pump and forces said content into a mixer and thorugh a riser tube, via a heat exchanger back into the reactor. The mixture is designed so that the feed contains a constricted pipe cross-section where a higher flow rate results and into whose turbulence zone a thin feed line is led axially and opposite to the direction of flow, through which feed line a defined amount of water can be fed in under 40 bar argon at regular intervals. The reaction is monitored by means of a sampler in the pumped circulation.
However, other reactors are in principle also suitable.
5 dm3 of decane are initially taken under inert conditions in the reactor described above and having a volume of 16 dm3. 0.5 dm3 (=5.2 mol) of trimethylaluminum are fed in at 25xc2x0 C. Thereafter, 250 g of silica gel SD 3216 30 (Grace AG), which was dried beforehand at 120xc2x0 C. in an argon fluidized bed, are metered into the reactor through a solids hopper and homogeneously distributed with the aid of the stirrer and of the pumping system. A total amount of 76.5 g of water is fed into the reactor in portions of 0.1 cm3 every 15 seconds in the course of 3.25 hours. The pressure, generated by the argon and the gases evolved, is kept constant at 10 bar by a pressure relief valve. After all the water has been introduced, the pumping system is switched off and stirring is continued for 5 hours at 25xc2x0 C.
The supported cocatalyst prepared in this manner is used as a 10% strength suspension in n-decane. The aluminum content is 1.06 mmol of Al per cm3 of suspension. The solid isolated contains 31% by weight of aluminum and the suspending medium contains 0.1% by weight of aluminum.
Further possibilities for preparing a supported cocatalyst are described in EP 578 838.
The novel metallocene is then applied to the supported cocatalyst by stirring the dissolved metallocene with the supported cocatalyst. The solvent is removed and is replaced by a hydrocarbon in which both the cocatalyst and the metallocene are insoluble.
The reaction to give the supported catalyst system is carried out at from xe2x88x9220 to +120xc2x0 C., preferably from 0 to 100xc2x0 C., particularly preferably from 15 to 40xc2x0 C. The metallocene is reacted with the supported cocatalyst by combining the cocatalyst as a from 1 to 40, preferably from 5 to 20, % strength by weight suspension in an aliphatic, inert suspending medium, such as n-decane, hexane, heptane or diesel oil, with a solution of the metallocene in an inert solvent, such as toluene, hexane, heptane or dichloromethane, or with the finely milled solid metallocene. Conversely, it is also possible to react a solution of the metallocene with the solid cocatalyst.
The reaction is carried out by thorough mixing, for example by stirring, at a molar Al/M1 ratio of 100/1 to 10,000/1, preferably from 100/1 to 3000/1, and with a reaction time of from 5 to 120, preferably from 10 to 60, particularly preferably from 10 to 30, minutes under inert conditions.
In the course of the reaction time for the preparation of the supported catalyst system, changes in the color of the reaction mixture occur, in particular with the use of the novel metallocenes having absorption maxima in the visible range, and the progress of the reaction can be monitored on the basis of said changes in the color.
After the reaction time has expired, the supernatant solution is separated off, for example by filtration or decanting. The solid remaining behind is washed from 1 to 5 times with an inert suspending medium, such as toluene, n-decane, hexane, diesel oil or dichloromethane, to remove soluble components in the catalyst formed, in particular to remove unconverted and hence soluble metallocene.
The supported catalyst system thus prepared, in the form of a powder after drying under reduced pressure or still in contact with the solvent, can be resuspended and metered as a suspension in one of the abovementioned inert suspending media into the polymerization system.
If the polymerization is carried out as a suspension or solution polymerization, an inert solvent customary for the Ziegler low-pressure process is used. For example, an aliphatic or cycloaliphatic hydrocarbon is employed. Examples of these are propane, butane, hexane, heptane, isooctane, cyclohexane and methylcyclohexane. A gasoline fraction or hydrogenated diesel oil fraction may furthermore be used. Toluene may also be used. Polymerization is preferably effected in the liquid monomer.
Before the addition of the catalyst, in particular of the supported catalyst system (containing the novel metallocene and a supported cocatalyst), another aluminum alkyl compound, for example trimethylaluminum, triethylaluminum, triisobutylaluminum, trioctylaluminum or isoprenylaluminum, may additionally be introduced into the reactor for rendering the polymerization system inert (for example for separating off catalyst poisons present in the olefin). This is added to the polymerization system in a concentration of from 100 to 0.01 mmol of Al per kg of reactor content. Triisobutylaluminum and triethylaluminum in a concentration of from 10 to 0.1 mmol of Al per kg of reactor content are preferred. As a result, a low molar Al/M1 ratio can be chosen in the synthesis of a supported catalyst system.
If inert solvents are used, the monomers are metered in in gaseous or liquid form.
The polymerization may be of any desired duration, since the catalyst system to be used in the novel process exhibits only a slight time-dependent decline in the polymerization activity.
The special stereorigid metallocene compounds described in the present invention are suitable for the preparation of polyolefins, in particular those having reduced crystallinity, high impact strength, high transparency, high flowability at the processing temperature and a reduced melting point.
The principal uses of such polyolefins are as plasticizers and lubricant formulations, hot-melt adhesives, coatings, sealants, insulations, casting materials or sound-insulation materials.
By using hydrogen or by increasing the polymerization temperature, it is also possible to obtain polyolefins having a lower molar mass, such as waxes, whose hardness or melting point can be varied by means of the comonomer content.
Conversely, by choosing the polymerization conditions, it is also possible to prepare high molecular weight polyolefins which are suitable as thermoplastic materials. These are suitable in particular for the production of moldings, such as films, sheets or large hollow articles (e.g. pipes).
By choosing the polymerization process and the type(s) of comonomers as well as the amount(s) of comonomers, olefin copolymers having elastomeric properties, e.g. ethylene/propylene/1,4-hexadiene terpolymers, can be prepared.
The examples which follow illustrate the invention.
Organometallic compounds were prepared and handled in the absence of air and moisture, under inert argon gas (Schlenk method). Before use, all solvents required were rendered absolutely dry by boiling for several hours over a suitable drying agent and then distilling under argon.
The preparation of the xcex1,xcex2-unsaturated ketones and fulvenes used as starting compound was carried out by methods known from the literature (Synlett (1991) 771; J. Chem. Soc., Commun. (1986) 1694; Chem. Ber. 116, (1983) 119; Tetrahedron Lett. 23; (1982) 1447); cyclopentadiene was obtained by cracking the dimer and was stored at xe2x88x9235xc2x0 C.
The compounds prepared were analyzed by 1H-NMR.